Abstract
Microbial-induced calcium carbonate precipitation (MICP) is a promising technique for strengthening soil. The influences calcium sources (calcium chloride, calcium acetate, and calcium nitrate) and seawater/freshwater environment on the improvement of coral sand were studied. A microbial-induced calcium carbonate precipitation (MICP) aqueous solution experiment was carried out to explore the influence of the different calcium source and seawater/freshwater on the relationship between calcium carbonate precipitation and time. Coral sand column treatment tests were conducted to investigate the environmental impact on soil strengthening. The results show that the actual production of calcium carbonate is 20% lower than the theoretical value. Calcium chloride was found to be the optimal calcium source in terms of the seawater environment affect 2% of calcium carbonate production compared with the freshwater environment. The results of tests on three different calcium sources (calcium chloride, calcium acetate, and calcium nitrate) showed that seawater adversely affected the unconfined compression strength (UCS) and the tensile splitting strength (TSS) of strengthened specimens compared with freshwater. The UCS and TSS values in the freshwater environment were approximately 30–45% higher than those in the seawater environment. Nevertheless the strengthened specimens in the seawater environment exhibited high strength, and the MICP improvement effect can be guaranteed. Therefore, The MICP technology can be used to improve coral sand for construction work in seawater environments.
Highlights
Biomineralization has been extensively studied over the recent decades [1–4]
The results of several coral sand column experiments were used to determine the effect of a seawater environment on samples treated with microbial-induced calcium carbonate precipitation (MICP) using different calcium sources
The objective of this paper was to study the influence of a seawater environment and different calcium sources on strengthening coral sand
Summary
The mechanism of microbial-induced calcium carbonate precipitation (MICP) involves bacterial hydrolysis of urea to metabolites, which react with ambient substances to produce a large quantity of precipitates. Studies have been performed to investigate the effects of microbial characteristics (including the type of bacteria), the cementation solution, temperature, salinity, and the pH on MICP-treated sand [7–13]. Different types of crystals are induced by different calcium sources [15, 16]. MICP has been studied as a potential solution to environmental problems and soil stabilization in many engineering fields, such as the remediation of heavy-metal-contaminated soil [17, 18], the mitigation of soil liquefaction [19–21], reduction of MICP in Sea Water Environment permeability and improve the durability of concretes material [22], the sequestration of atmospheric CO2 [23], and the suppression of sand dust emissions [24]
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